A new sialic acid analogue, 9-O-acetyl-deaminated neuraminic acid, and alpha -2,8-linked O-acetylated poly(N-glycolylneuraminyl) chains in a novel polysialoglycoprotein from salmon eggs.
A new polysialoglycoprotein, designated PSGP(On), was isolated from the unfertilized eggs of the kokanee salmon, Oncorhynchus nerka adonis. 400-MHz 1H NMR analyses showed the O. nerka adonis PSGP contained alpha -2,8-linked oligo- and polysialic acid (polySia) chains that were made up of 4-O-Ac-, 7-O-Ac-, and 9-O-Ac esters of N-glycolylneuraminic acid (Neu5Gc) residues. The presence of a new sialic acid derivative, identified by 1H NMR as 9-O-acetyl-2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (trivial name, 9-O-acetyldeaminated neuraminic acid; 9-O-Ac-KDN), was also shown to be present as a minor component. The O-acetylated KDN residues appear to cap the nonreducing termini of the O-acetylated poly(Neu5Gc) chains. The O-acetylated polySia chains were resistant to depolymerization by bacterial exosialidases and a bacteriophage-derived endo-N-acylneuraminidase that is specific for catalyzing the hydrolysis of alpha -2,8-linkages in polySia containing either N-acetylneuraminic acid or Neu5Gc residues. After de-O-acetylation by mild alkali, the polySia chains were sensitive to digestion by endo-N-acylneuraminidase, yet partially resistant to exosialidase. These data confirm the alpha -2,8-ketosidic linkage in these chains and the nonreducing terminal location of the KDN residues. These results extend further the range of structural diversity in polySia-containing glycoconjugates, and in the family of naturally occurring sialic acids. They also suggest that the O-acetylated Neu5Gc and 9-O-Ac-KDN residues may have an important role during oogenesis.
Iwasaki
M
M
School of Pharmaceutical Sciences, Showa University, Tokyo, Japan.
Inoue
S
S
Troy
F A
FA
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002240:Carbohydrate Sequence; D002241:Carbohydrates / Q000032:analysis; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D002855:Chromatography, Thin Layer; D005260:Female; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009438:Neuraminic Acids / Q000032:analysis*; D009439:Neuraminidase; D009844:Oligosaccharides / Q000302:isolation & purification; D010063:Ovum / Q000032:analysis; D012474:Salmon; D012795:Sialoglycoproteins / Q000032:analysis*; D013045:Species Specificity
D000596:Amino Acids; D002241:Carbohydrates; D009438:Neuraminic Acids; D009844:Oligosaccharides; D012795:Sialoglycoproteins; C063056:9-O-acetyl-2-keto-3-deoxyglycero-galacto-nononic acid; D009439:Neuraminidase